Time and again Thanos has been defeated, with attempts to show he's not all that and then Starlin keeps writing in retcons, despite the fact it's a joke.

That's what is amusing. No one takes Squirrel Girl seriously, it's just funny how, an actual panel was added just to counter that.

It's not like we think the NYPD are herald level characters and that's how they captured Thanos.

But yes, Superman has beaten Darkseid and Squirrel Girl hasn't quite beat the original Thanos, so a more impressive showing from Superman. I am not trying to reduce your evidence that Superman is above Marvel top tiers here.

Not sure how two retcons is “time and time again”. The third retcon didn’t even involve a defeat IIRC. Neither of the two loses involve straight up head to head defeats and Starlin himself has written Thanos being defeated. Starlin’s retcons were about characterization. He didn’t want a nihilistic Thanos anymore.

Dan Slott wrote Squirrel Girl defeating Thanos and he also wrote the retcon. So that was not Starlin’s doing, but rather a writer poking fun at Starlin and retconning his own story.

And since Superman struggled more against Thor than he did Darkseid in Apokolips Now, we can agree tha Thor is above DC top tiers.